1. Field of the Invention
The present invention relates to a leak sealing composition for refrigeration systems, and more particularly to a composition and method for repairing air conditioners using Freon.RTM. and refrigerators without replacement of parts.
2. Brief Description of the Prior Art
The use of refrigeration systems using Freon.RTM. is now universal in the United States for automobile air conditioning, home refrigerators, home freezers, and building air conditioners. As is well known, such systems are sealed and circulate the Freon.RTM. refrigerant by means of a compressor. Although every practical effort is made by the manufacturer to provide a leakproof system, this is not practical. No joints are perfect, and the materials used in the system have a leakage factor. Leakage is also two-way; Freon.RTM. leaks out and air leaks in.
Although generally minute, some infiltration occurs through hose walls. Seals in the compressor permit a small leakage, and the joints are also trouble spots. Fortunately, these small leaks do not cause failure of the system and, if no other problems occur, the system may operate for several years. However, problems arise when water vapor leaks into the system. When this happens, the water reacts chemically with the Freon.RTM. to form various acids, such as hydrochloric acid. The acid circulates with the refrigerant and can, of course, damage metal parts of the system. The evaporator is especially vulnerable for two reasons; its walls are very thin, and once the acid droplets enter, they are trapped due to their inability to evaporate. The drops separate from the Freon.RTM. and begin to corrode the inner surfaces of the evaporator core.
When a hole forms through the evaporator wall, excessive loss of Freon.RTM. occurs and rapid loss of efficiency or complete failure of the system can result.
Some air conditioners are more prone to this problem than others. For example, in the automobile air conditioning industry, the evaporators in General Motors automobiles began to fail at an abnormally high rate in the 1977 model year. The problem turned out to be acid-caused pinholes through the aluminum walls. As a result of this problem, a rebuilding industry developed in which replaced evaporator cores were reworked and the leaks repaired using a variety of techniques. Some rebuilders patch leaks by embedding the lower portions of the core in epoxy, while others coat the interior surfaces with a very thin epoxy coat. Liquid rubber and fiberglass have also been used. Regardless of the method of rebuilding, the cost to the consumer to have an evaporator replaced is quite high. When leaks occur in refrigerators and freezers, it is usually impractical to replace or repair due to the location of the failed elements within the cabinet walls.
Thus, there is a long felt need for a leak sealing material and method that can repair pinhole leaks and the like in refrigeration systems without replacing components.
Leak sealing compositions have been known in the prior art for automobile cooling systems. For example, U.S. Pat. No. 3,630,914 to Noukee et al teaches the use of cross-linked polyacrylamide particles in the range of 50 mesh to 200 mesh added to the coolant. The particles tend to swell in the presence of water and to thereby stop leaks. Martin, in U.S. Pat. No. 3,692,549, utilizes flax mixed with graphite and aluminum powder, although he notes powdered iron, magnesium, calcium, manganese, or copper may be used. This composition is suitable for stopping leaks in aqueous solutions. U.S. Pat. No. 3,984,339 to Takeo, et al shows the use of cellulose particles in electrical insulating oil for stopping leaks internally in oil cooling systems. However, none of these compositions are suitable for injecting into the Freon.RTM. circuit of a refrigeration system.